Method, system, and device for user detachment when a handover or change occurs in heterogeneous network

ABSTRACT

A method for user detachment when a handover or change occurs in a heterogeneous network is provided. The method includes: a user equipment (UE) is handed over or switched from a source network to a target network; a network element on a network side determines whether to detach the UE from the source network, and if yes, the network element on the network side detaches the UE from the source network. A system and a device for user detachment when a handover or change occurs in a heterogeneous network, and another method for user detachment when a handover or change occurs in a heterogeneous network are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/952,938, filed on Jul. 29, 2013, which is a continuation of U.S.patent application Ser. No. 12/479,216, filed on Jun. 5, 2009. U.S.patent application Ser. No. 12/479,216 is a continuation ofInternational Patent Application No. PCT/CN2008/071842, filed on Jul.31, 2008. The International Patent Application claims priority toChinese Patent Application No. 200710137568.8, filed on Aug. 7, 2007.The afore-mentioned patent applications are hereby incorporated byreference in their entireties.

FIELD OF THE TECHNOLOGY

The present invention relates to the network communication technologyand more particularly to a method, system, and device for userdetachment when a handover or change occurs in a heterogeneous network.

BACKGROUND

To improve the competitiveness of networks in the future, a newevolution network is now researched for a 3rd-generation partnershipproject (3GPP) network. FIG. 1 is a schematic structural view of anevolution network system for a 3GPP network. The system includes: anevolved UMTS terrestrial radio access network (E-UTRAN), forimplementing all functions related to the wireless feature of theevolution network; a mobility management entity (MME), for mobilitymanagement of a control plane, including management of a user contextand a mobility state and allocation of temporary user identities; aserving gateway (serving GW) entity, for acting as a user plane anchorpoint between access networks of the 3GPP network for terminating theE-UTRAN; a packet data network gateway (PDN GW) entity, for acting as auser anchor point between an access network of the 3GPP network and anaccess network of a non-3GPP network, and an interface for terminatingthe external PDN; a policy and charging rule function (PCRF) entity, forimplementing functions of policy control decision and flow-basedcharging control; and a home subscriber server (HSS), for storingsubscription information of users.

The UMTS terrestrial radio access network (UTRAN) or GSM/EDGE radioaccess network (GERAN) implements all functions relevant to the wirelessfeature of the existing UMTS/GPRS network; a serving GPRS supportingnode (SGSN) implements functions of route forwarding, mobilitymanagement, session management, and user information storage in theGPRS/UMTS network.

IP access networks of the non-3GPP network mainly include accessnetworks defined by non-3GPP network organizations, for example,wireless local area network (WLAN), worldwide interoperability formicrowave access (Wimax), and code division multiple access (CDMA)network.

An authentication, authorization, and accounting server (AAA server)mainly implements access authentication, authorization, and accountingfor user equipment (UE).

It should be noted that, the schematic structural view of FIG. 1 is notthe only schematic structural view of the evolution network system for a3GPP network. The evolution network of a 3GPP network may have variousstructures.

One requirement on the evolution network of a 3GPP network is to realizethe handover or switching of the UE between a 3GPP network and anon-3GPP network. FIG. 2 is a flow chart of a process that the UE ishanded over or switched from a 3GPP network to a non-3GPP network in theprior art. The process includes the following steps.

In Step 201, the UE accesses the 3GPP network through a serving GW and aPDN GW.

In FIG. 2, the mobility management network element (MME) and the servingGW belong to the 3GPP network, a non-3GPP GW belongs to the non-3GPPnetwork, and the PDN GW and HSS/AAA server are common network elementsshared by the 3GPP network and the non-3GPP network.

In Step 202, the UE triggers the handover or switching from the 3GPPnetwork to the non-3GPP network.

In Step 203, the UE sends an Access Request message to the non-3GPP GW,and requests to access the non-3GPP GW.

As for a WLAN system, the non-3GPP GW in this step is an evolved packetdata gateway (EPDG); as for a Wimax system, the non-3GPP GW in this stepis an access service network gateway (ASN GW); and as for a CDMA system,the non-3GPP GW is an access gateway (AGW).

In Step 204, an access authentication process is performed between theUE, the non-3GPP GW, and the HSS/AAA server, and the non-3GPP GW obtainsthe PDN GW address information used by the UE.

In Step 205 a, the non-3GPP GW sends a proxy binding update message tothe PDN GW.

In this step, it is assumed that an interface protocol between thenon-3GPP GW and the PDN GW is the proxy mobile internet protocol (PMIP).If an interface protocol between the UE and the PDN GW is the clientmobile internet protocol (CMIP), Step 205 a is replaced by Step 205 b,in which the UE sends a binding update message to the PDN GW.

In Step 206 a, the PDN GW sends a proxy binding acknowledgement messageto the non-3GPP GW.

In this step, it is assumed that the interface protocol between thenon-3GPP GW and the PDN GW is the PMIP. If the interface protocolbetween the UE and the PDN GW is the CMIP, Step 206 a is replaced byStep 206 b, in which the PDN GW sends a binding Ack message to the UE.

In Step 207, the non-3GPP GW returns an access accept message to the UE.

In Step 208, the PDN GW sends a delete bearer request message to theserving GW, and the serving GW sends the delete bearer request messageto the MME.

In Step 209, the MME deletes bearer resources related to the UE, returnsa delete bearer response message to the serving GW, and the serving GWreturns the delete bearer response message to the PDN GW.

The above flow is a specific example of the process that the UE ishanded over or switched from a 3GPP network to a non-3GPP network.Certainly, the handover or change process is not limited to the abovedescriptions. A 3GPP network involved in the handover or change may beGERAN, UTRAN, or EUTRAN. A non-3GPP network involved in the handover orchange may be WLAN, Wimax, or CDMA system.

Once the UE accesses a 3GPP network, the 3GPP network creates bearerresources of the UE and a mobility management context of the UE. Themobility management context of the UE exists in the MME. Furthermore,bearer resources of a 3GPP network and a mobility management context ofa 3GPP network are also created in the UE. Therefore, when the UE ishanded over or switched from a 3GPP network to a non-3GPP network, userdetachment needs to be performed to save network resources. The userdetachment includes detachment of the 3GPP network and detachment of theUE. The detachment of the 3GPP network indicates that the 3GPP networkdeletes the bearer resources of the UE and the mobility managementcontext of the UE, and the detachment of the UE indicates that the UEdeletes the bearer resources of the 3GPP network and the mobilitymanagement context of the 3GPP network. Here, the mobility managementcontext of the UE exists in the MME.

However, in the process shown in FIG. 2, when the UE is handed over orswitched from a 3GPP network to a non-3GPP network, the 3GPP networkmerely deletes the bearer resources of the UE, but does not delete themobility management context of the UE, and meanwhile, the UE does notdelete the bearer resources and mobility management context of the 3GPPnetwork as well.

As known from the above that, the prior art neither provides a methodfor 3GPP network detachment when the UE is handed over or switched froma 3GPP network to a non-3GPP network, nor provides a specific method foruser detachment of the UE when the UE is handed over or switched from a3GPP network to a non-3GPP network. That is to say, no specific solutionfor user detachment when handover or change occurs in a heterogeneousnetwork is provided in the prior art.

In addition, if the UE has a single radio capability, that is, the UEcan access only one network, after the UE is handed over or switchedfrom a 3GPP network to a non-3GPP network, user detachment needs to beperformed, that is, the 3GPP network needs to detach the UE, and the UEneeds to be detached from the 3GPP network. The detaching, by the 3GPPnetwork, the UE includes that the 3GPP network deletes the bearerresources of the UE on the 3GPP network side, and the mobilitymanagement context of the UE in the MME. The detaching, by the UE, fromthe 3GPP network includes that the UE deletes the bearer resources andmobility management context created when the UE accesses the 3GPPnetwork.

If the UE has a dual radio capability, that is, the UE can access twonetworks at the same time, after the UE is handed over or switched froma 3GPP network to a non-3GPP network, it is judged whether the 3GPPnetwork needs to detach the UE according to, for example, information ofoperator policies. In other words, the prior art does not provide asolution for determining whether to perform the user detachment when theUE is handed over or switched from a 3GPP network to a non-3GPP network.

To sum up, during researches and applications, the inventor(s) of thepresent invention finds that the prior art has at least the followingproblems: the prior art neither provides a specific solution for userdetachment when a handover or change occurs in a heterogeneous network,nor provides a solution for judging whether to perform user detachmentwhen handover or change occurs in a heterogeneous network.

SUMMARY

An embodiment of the present invention provides a method for detaching auser when a handover or change occurs in a heterogeneous network.

An embodiment of the present invention further provides another methodfor detaching a user when a handover or change occurs in a heterogeneousnetwork.

An embodiment of the present invention provides a system for detaching auser when a handover or change occurs in a heterogeneous network.

An embodiment of the present invention provides a device for detaching auser when a handover or change occurs in a heterogeneous network.

An embodiment of the present invention further provides a device fordetaching a user when a handover or change occurs in a heterogeneousnetwork.

A method for detaching a user when handover or change occurs in aheterogeneous network includes the following steps.

First, a UE is handed over or switched from a source network to a targetnetwork.

Next, a network element on a network side determines whether to detachthe UE from the source network; if yes, the UE is detached from thesource network.

Another method for user detachment when a handover or change occurs in aheterogeneous network includes the following steps.

First, a UE triggers handover or switching from a source network to atarget network.

Next, the UE determines whether to be detached from the source network;if yes, the UE is detached from the source network.

A system for user detachment when a handover or change occurs in aheterogeneous network includes a UE and a network side.

The UE is adapted to be handed over or switched from a source network onthe network side to a target network on the network side.

The network side is adapted to hand over or switch the UE from thesource network to the target network, and detach the UE from the sourcenetwork.

A device for detaching a user when a handover or change occurs in aheterogeneous network includes a second handover or change module and asecond detachment module on a network side.

The second handover or switching module is adapted to hand over orswitch a UE from a source network on the network side to a targetnetwork on the network side.

The second detachment module is adapted to detach the UE from the sourcenetwork.

A device for detaching a user when a handover or change occurs in aheterogeneous network includes a first handover or change module and afirst detachment module in a UE.

The first handover or change module is adapted to hand over or switchthe UE from a source network to a target network;

The first detachment module is adapted to detach the UE from the sourcenetwork.

As known from the above solutions that, in the embodiments of thepresent invention, when a handover or change occurs in the heterogeneousnetwork, the UE is detached from the source network after beingdetermined by the source network or the UE is detached from the sourcenetwork after being determined by the UE. Thus, detachment of the useris realized by the source network or the UE, when the handover or changeoccurs in the heterogeneous network.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural view of an evolution network system fora 3GPP network in the prior art;

FIG. 2 is a flow chart of a process that the UE is handed over orswitched from a 3GPP network to a non-3GPP network in the prior art;

FIG. 3 is a flow chart of a process that a network element in a 3GPPnetwork acquires terminal capability of UE and access policy informationof an operator when the UE accesses the 3GPP network according to anembodiment of the present invention;

FIG. 4 is a flow chart of a process that a network element in a 3GPPnetwork acquires terminal capability of UE and access policy informationof an operator when a location area or terminal capability of the UEchanges according to an embodiment of the present invention;

FIG. 5 is a flow chart of a process that a network element in a non-3GPPnetwork acquires terminal capability of UE and access policy informationof an operator when the UE accesses the non-3GPP network according to anembodiment of the present invention;

FIG. 6 shows a first example of a method for user detachment when ahandover or change occurs in a heterogeneous network according to anembodiment of the present invention;

FIG. 7 shows a second example of the method for user detachment when ahandover or change occurs in a heterogeneous network according to anembodiment of the present invention;

FIG. 8 shows a third example of the method for user detachment when ahandover or change occurs in a heterogeneous network according to anembodiment of the present invention;

FIG. 9 shows a fourth example of the method for user detachment when ahandover or change occurs in a heterogeneous network according to anembodiment of the present invention;

FIG. 10 shows a fifth example of the method for user detachment when ahandover or change occurs in a heterogeneous network according to anembodiment of the present invention;

FIG. 11 shows a sixth example of the method for user detachment when ahandover or change occurs in a heterogeneous network according to anembodiment of the present invention; and

FIG. 12 is a schematic structural view of a system for user detachmentwhen a handover or change occurs in a heterogeneous network according toan embodiment of the present invention.

DETAILED DESCRIPTION

To make the objectives, technical solutions, and beneficial effects ofthe present invention more comprehensible, the present invention isdescribed in detail below with reference to the accompanying drawingsand embodiments.

FIGS. 6-10 respectively show the first to fifth examples of a method foruser detachment when a handover or change occurs in a heterogeneousnetwork according to an embodiment of the present invention. The mainideas of the examples are described as follows:

The UE is handed over or switched from a source network to a targetnetwork; the source network determines whether to detach the UE from thesource network; if yes, the UE will be detached from the source network;otherwise, the UE will not be detached from the source network.

FIG. 11 shows a sixth example of a method for user detachment when ahandover or change occurs in a heterogeneous network according to anembodiment of the present invention. The main idea of this example isdescribed as follows.

The UE triggers a handover or switching from a source network to atarget network; the UE determines whether to be detached from the sourcenetwork; if yes, the UE will be detached from the source network;otherwise, the UE will not be detached from the source network.

The two networks involved in the handover or change in the heterogeneousnetwork according to the embodiments of the present invention may be oneof the 3GPP networks (such as a GERAN network, a UTRAN network, or anEUTRAN network) and one of the non-3GPP networks (such as a WLANnetwork, Wimax network, or CDMA network). Specifically, the embodimentsinclude the handover or switching of the UE from a 3GPP network to anon-3GPP network or the handover or switching of the UE from a non-3GPPnetwork to a 3GPP network. Here, the network where the UE originallyexists during the handover or change process is referred to as thesource network, and the other network involved in the handover or changeprocess is referred as the target network.

Then, the handover or switching from a 3GPP network to a non-3GPPnetwork is taken as an example to illustrate the first embodiment to thesixth embodiment of the method for UE detachment when a handover orchange occurs in the heterogeneous network of the present invention.

The UE and the network element in the 3GPP network acquire the terminalcapability of the UE, and the network element obtains access policyinformation of the operator, which are provided for being used in thesolution for UE detachment when the UE is handed over or switched fromthe 3GPP network to the non-3GPP network according to the embodiments ofthe present invention. Here, FIGS. 3 and 4 are used to illustrate theprocess that the network element in a 3GPP network acquires the terminalcapability of the UE and the access policy information of the operatoraccording to the embodiments of the present invention. FIG. 3 is a flowchart of a process that a network element in a 3GPP network acquiresterminal capability of UE and access policy information of an operatorwhen the UE accesses the 3GPP network. FIG. 4 is a flow chart of aprocess that a network element in a 3GPP network acquires terminalcapability of UE and access policy information of an operator when alocation area or terminal capability of the UE changes after the UEaccesses the 3GPP network according to an embodiment of the presentinvention.

Referring to FIG. 3, the process that the network element in the 3GPPnetwork acquires the terminal capability of the UE and the access policyinformation of the operator when the UE accesses the 3GPP networkincludes the following steps.

In step 301, the UE sends an attach request message carrying terminalcapability of the UE to the MME.

In this step, if the access network of the UE is GERAN/UTRAN, the SGSNserves as the MME; if the access network of the UE is EUTRAN, the MMEserves as the MME.

In this step, the terminal capability of the UE is represented byinformation element (IE) of the radio capability supported by the UE.The radio capability supported by the UE is a single radio capability(which indicates that the UE can access only one network at a certaintime point) or a dual radio capability (which indicates that the UE canaccess two or more networks at a certain time point). An exemplarystructure of the IE carrying the radio capability supported by the UE islisted as follows. The IE includes a radio capability parametersupported by the UE. The parameter may be: 1) the UE has a single radiocapability; 2) the UE has a dual radio capability.

<UE Network Capability value part> ::= UE Support Radio Capability...... UE Support Radio Capability 0 Single Radio Capability 1 DualRadio Capability

In step 302, the UE, the MME, and the HSS/AAA server implement anauthentication process of the UE to authenticate the UE.

In step 303, if the MME finds that the UE is in an invalid state, theMME sends an update location message to the HSS/AAA server, andregisters the UE with the HSS/AAA server. The update location messagecarries the terminal capability of the UE.

In this step, if the access policy information of the operator isconfigured in the MME, the update location request may carry the accesspolicy information of the operator. The access policy information of theoperator includes: 1) a single radio access, that is, the UE can accessonly one access network at a certain time point; and 2) a dual radioaccess, that is, the UE can access a plurality of access networks at acertain time point.

In step 304, the HSS/AAA server inserts subscription data of a user intothe MME.

In this step, if the access policy information of the operator isconfigured or subscribed in the HSS/AAA server, the HSS/AAA servercarries the access policy information of the operator in thesubscription data, and sends the subscription data to the MME.

In step 305, the HSS/AAA server returns an update location Ack messageto the MME.

In Step 306, the MME sends a create bearer request message to theserving GW, and the serving GW sends the create bearer request messageto the PDN GW.

In this step, the MME initiates a default bearer establishment process,so as to create a default bearer of the UE in the MME, serving GW, andPDN GW. The create bearer request message further carries a bearer typeIE. The MME uses the bearer type IE to notify the created bearer type tothe serving GW and the PDN GW. If the MME sets the bearer type IE todefault bearer, the serving GW and the PDN GW are notified that thecreated bearer is a default bearer.

In this step, the terminal capability of the UE and the access policyinformation of the operator are carried in the create bearer requestmessage and sent to the serving GW and the PDN GW.

Steps 307 and 308 are performed only when the policy and charging rulesused by the default bearer need to be obtained from the PCRF, and theaccess policy information of the operator is configured in the PCRF.

In step 307, the PDN GW sends a PCC rules request message to the PCRF toobtain the policy and charging rules used by the default bearer.

In step 308, the PCRF returns a PCC rules provision message to the PDNGW, and the PCC rules provision message carries the access policyinformation of the operator.

In step 309, the PDN GW and the serving GW create a bearer context, andsets the created bearer as the default bearer; the PDN GW returns acreate bearer response message to the serving GW, and the serving GWreturns the create bearer response message to the MME.

If the access policy information of the operator is configured in thePCRF entity, or the access policy information of the operator isconfigured in the PDN GW, or the access policy information of theoperator is configured in the serving GW, this step includes thefollowing: the create bearer response message carries the access policyinformation of the operator configured by the PCRF, the PDN GW, or theserving GW.

In this step, the bearer context created by the PDN GW and the servingGW includes bearer type information, which has two values: defaultbearer and dedicated bearer. For the default bearer, the PDN GW and theserving GW set the bearer type information in the bearer context todefault bearer. The PDN GW and the serving GW may know that the createdbearer is a default bearer in the following two manners.

1) In step 306, the MME carries the bearer type IE in the create bearerrequest message, and notifies the bearer type to the serving GW and thePDN GW through the bearer type IE. If the carried bearer type IE set bythe MME is in the value of default bearer, the created bearer is thedefault bearer.

2) The serving GW and the PDN GW determine whether the created bearer isthe first bearer created in the packet data network (PDN); if yes, theserving GW and the PDN GW determine that the created bearer is a defaultbearer.

Other bearers are dedicated bearers. In this case, the serving GW andthe PDN GW set the bearer type information in the bearer context todedicated bearer.

Step 310 a is performed only when the access network type (RAT type)information in the 3GPP network has been registered with the HSS/AAAserver by the MME.

In step 310 a, the MME registers access situations of the UE in the 3GPPnetwork (for example, the RAT type used by the UE) with the HSS/AAAserver.

Step 310 b is performed only when the RAT type information of the UE inthe 3GPP network has been registered with the HSS/AAA server by the PDNGW.

In step 310 b, the PDN GW registers the access situations of the UE inthe 3GPP network (for example, the RAT type used by the UE) with theHSS/AAA server.

Through this step, the HSS/AAA server obtains the access networksituations of the UE. For example, in this embodiment, the HSS/AAAserver knows that the RAT type of the UE is a 3GPP network type, or aspecific network type in a 3GPP network.

The RAT type of the UE includes the following two situations.

1) The RAT type of the UE is categorized into a 3GPP network and anon-3GPP network.

2) The RAT type of the UE is a specific network type used by the UE, forexample, GERAN network, UTRAN network, EUTRAN network, WLAN network,Wimax network, CDMA network, etc.

In Step 311, the MME returns an Attach Accept message to a networkelement on an access side, and the Attach Accept message carriesinformation of the radio bearer to be established by the UE.

As for the EUTRAN access network, the network element on the access sideis ENodeB; as for the UTRAN access network, the network element on theaccess side is RNC; as for the GERAN access network, the network elementon the access side is BSS. The MME may carry the access policyinformation of the operator in the Attach Accept message.

In step 312, the network element on the access side sends a bearerestablishment request message to the UE, and requests the UE toestablish a radio bearer. The message carries the access policyinformation of the operator sent by the MME.

The access policy information of the operator may also be notified tothe UE in a broadcast message of a cell.

In step 313, the UE establishes the bearer context, sets the createdbearer to a default bearer, and returns a radio bearer establishmentresponse message to the network element on the access side.

The UE adds bearer type information to the established bearer context,and the bear type has the following two values: default bearer anddedicated bearer. For the default bearer, the UE sets the bearer typeinformation in the bearer context to default bearer. The bearer typeadded to the established bearer context by the UE may be acquiredthrough the following manners.

1) In step 311, the MME carries a bearer type IE in the Attach Acceptmessage, and notifies the bearer type to the UE by the network elementon the access side through the bearer type IE. For the default bearer,the value of the bearer type IE carried by the MME is Default Bearer.

2) The UE determines whether the created bearer is the first bearercreated in the PDN; if yes, the UE determines that the created bearer isa default bearer.

Other bearers are dedicated bearers. In this case, the UE sets thebearer type information in the bearer context to dedicated bearer.

In this embodiment, it should be noted that, the HSS and the AAA servermay be configured in different entities or in a same entity. If the HSSand the AAA server are configured in different entities, the registermessage sent by the PDN GW in step 310 a is forwarded to the HSS by theAAA server, and the register message sent by the MME in step 310 b isforwarded to the AAA server by the HSS.

FIG. 4 is a flow chart of a process that a network element in a 3GPPnetwork acquires terminal capability of UE and access policy informationof an operator when a location area or terminal capability of the UEchanges. The process includes the following steps.

In step 401, the UE sends a tracking area update or routing area updaterequest (TAU/RAU request) message carrying changed terminal capabilityof the UE to the MME.

If the access network of the UE is GERAN/UTRAN, the message sent by theUE is the RAU request message; if the access network of the UE isEUTRAN, the message sent by the UE is the TAU request message.

The terminal capability of the UE is represented by IEs of the radiocapability supported by the UE. The radio capability supported by the UEis a single radio capability (which indicates that the UE can accessonly one network at a certain time point) or a dual radio capability(which indicates that the UE can access two or more networks at acertain time point). An exemplary structure of the IE carrying the radiocapability supported by the UE is listed as follows. The IE includes aradio capability parameter supported by the UE. The parameter may be: 1)the UE has a single radio capability; 2) the UE has a dual radiocapability.

<UE Network Capability value part> ::= UE Support Radio Capability...... UE Support Radio Capability 0 Single Radio Capability 1 DualRadio Capability

In step 402, the MME sends an update location message to the HSS/AAAserver, and registers the UE with the HSS/AAA server, in which theupdate location message carries the changed terminal capability of theUE.

In this step, if the access policy information of the operator isconfigured in the MME, the update location request message carries theaccess policy information of the operator. The access policy informationof the operator includes: 1) a single radio access, that is, the UE canaccess only one access network at a certain time point; and 2) a dualradio access, that is, the UE can access a plurality of access networksat a certain time point.

In step 403, the HSS/AAA server inserts subscription data of a user intothe MME.

In this step, if the access policy information of the operator isconfigured or subscribed in the HSS/AAA server, the HSS/AAA serverdelivers the changed access policy information of the operator to theMME.

In Step 404, the HSS/AAA server returns an update location Ack messageto the MME.

In Step 405, when the MME determines that the access policy informationof the operator and the terminal capability of the UE has changed, theMME sends an update bearer request message to the serving GW, and theserving GW sends the update bearer request message to the PDN GW, inwhich the update bearer request message carries the changed accesspolicy information of the operator and the changed terminal capabilityof the UE.

In this step, the changed access policy information of the operator andthe changed terminal capability of the UE are notified to the serving GWand the PDN GW.

Step 406 a is performed only when the RAT type information in the 3GPPnetwork has been registered with the HSS/AAA server by the MME and theinformation has changed.

In Step 406 a, the MME registers the access situations of the UE in the3GPP network (for example, the RAT type used by the UE) with the HSS/AAAserver.

Step 406 b is performed only when the RAT type information in the 3GPPnetwork has been registered with the HSS/AAA server by the PDN GW andthe information has changed.

In step 406 b, if the RAT type information in the 3GPP network has beenregistered with the HSS/AAA server by the PDN GW and the information haschanged, the PDN GW registers the access situations of the UE in the3GPP network (for example, the RAT type used by the UE) with the HSS/AAAserver.

In step 407, the MME returns a TAU/RAU accept message to the UE, and theMME may deliver the changed access policy information of the operator tothe UE in the TAU/RAU accept message.

The changed access policy information of the operator may also benotified to the UE in a broadcast message of the cell.

FIG. 4 shows the process that the network element in a 3GPP networkacquires the changed terminal capability of the UE and the changedaccess policy information of the operator when the terminal capabilityof the UE and the access policy information of the operator both havechanged. The process that the network element in the 3GPP networkacquires the changed terminal capability of the UE or the changed accesspolicy information of the operator when the terminal capability of theUE or the access policy information of the operator has changed issimilar to the process of FIG. 4, which thus is not described in detailhere.

The UE and the network element in a non-3GPP network acquire theterminal capability of the UE, and the network element acquires theaccess policy information of the operator, which are provided for beingused in the solution for UE detachment when the UE is handed over orswitched from the non-3GPP network to a 3GPP network according to theembodiments of the present invention. FIG. 5 is used to illustrate theprocess that the network element in a non-3GPP network acquires theterminal capability of the UE and the access policy information of theoperator according to the embodiments of the present invention. FIG. 5is a flow chart of a process that a network element in a non-3GPPnetwork acquires terminal capability of UE and access policy informationof an operator when the UE accesses the non-3GPP network.

Referring to FIG. 5, the process that the network element in thenon-3GPP network acquires the terminal capability of the UE and theaccess policy information of the operator when the UE accesses thenon-3GPP network includes the following steps.

In step 501, the UE sends an access request message carrying theterminal capability of the UE to a non-3GPP GW.

In this step, if the non-3GPP network is a WLAN network, the non-3GPP GWis an EPDG; if the non-3GPP network is a Wimax network, the non-3GPP GWis an ASN GW; and if the non-3GPP network is a CDMA network, thenon-3GPP GW is an AGW.

In this step, the terminal capability of the UE is represented by IEs ofthe radio capability supported by the UE. The radio capability supportedby the UE is a single radio capability (which indicates that the UE canaccess only one network at a certain time point) or a dual radiocapability (which indicates that the UE can access two or more networksat a certain time point). An exemplary structure of the IE carrying theradio capability supported by the UE is listed as follows. The IEincludes a radio capability parameter supported by the UE. The parametermay be: 1) the UE has a single radio capability; 2) the UE has a dualradio capability.

<UE Network Capability value part> ::= UE Support Radio Capability...... UE Support Radio Capability 0 Single Radio Capability 1 DualRadio Capability

In step 502, an authentication process is performed between the UE, thenon-3GPP GW, and the HSS/AAA server.

In this step, if the access policy information of the operator isconfigured in the non-3GPP GW, an access authentication message maycarry the access policy information of the operator to the HSS/AAAserver. The access policy information of the operator includes: 1) asingle radio access, that is, the UE can access only one access networkat a certain time point; and 2) a dual radio access, that is, the UE canaccess a plurality of access networks at a certain time point. In thisstep, if the access policy information of the operator is configured inthe HSS/AAA server, the access authentication message may carry theaccess policy information of the operator to the non-3GPP GW.

In step 503 a, the non-3GPP GW sends a proxy binding update message tothe PDN GW.

In this step, it is assumed that an interface protocol between thenon-3GPP GW and the PDN GW is the proxy mobile internet protocol (PMIP).If an interface protocol between the UE and the PDN GW is the clientmobile internet protocol (CMIP), step 503 a is replaced by step 503 b,in which the UE sends a binding update message to the PDN GW.

In this step, the terminal capability of the UE and the access policyinformation of the operator may be carried in the proxy binding updatemessage or the binding update message and sent to the PDN GW.

In step 504, if the policy and charging rules used by the UE need to beobtained from the PCRF, the PDN GW sends a PCC rules request message tothe PCRF to obtain the policy and charging rules used by the UE.

In step 505, the PCRF provides a PCC rules provision message of thepolicy and charging rules used by the UE to the PDN GW. If the accesspolicy information of the operator is configured in the PCRF, the PCRFtransmits the access policy information of the operator to the PDN GWvia the PCC rules provision message.

In step 506, if the policy and charging rules used by the UE need to beobtained from the PCRF, the non-3GPP GW sends a PCC rules requestmessage to the PCRF to obtain the policy and charging rules used by theUE.

In step 507, the PCRF provides a PCC rules provision message of thepolicy and charging rules used by the UE to the non-3GPP GW. If theaccess policy information of the operator is configured in the PCRF, thePCRF transmits the access policy information of the operator to thenon-3GPP GW via the PCC rules provision message.

In step 508 a, the PDN GW sends a proxy binding Ack message to thenon-3GPP GW.

In this step, it is assumed that the interface protocol between thenon-3GPP GW and the PDN GW is the PMIP. If the interface protocolbetween the UE and the PDN GW is the CMIP, step 508 a is replaced bystep 508 b, in which the PDN GW sends a binding Ack message to the UE.

In step 509, if the RAT type information in the non-3GPP network isregistered with the HSS/AAA server by the PDN GW, the PDN GW registersthe access situations of the UE in the non-3GPP network (for example,the RAT type used by the UE) with the HSS/AAA server.

In step 510, if the RAT type information in the non-3GPP network isregistered with the HSS/AAA server by the non-3GPP GW, the non-3GPP GWregisters the access situations of the UE in the non-3GPP network (forexample, the RAT type used by the UE) with the HS S/AAA server.

Through step 509 or step 510, the HSS/AAA server obtains the accessnetwork situations of the UE. For example, in this embodiment, theHSS/AAA server knows that the RAT type of the UE is a non-3GPP networktype, or a specific network type in the non-3GPP network. This step isoptional.

The RAT type used by the UE may be processed through the following twomanners.

1) The RAT type used by the UE is categorized into a 3GPP network and anon-3GPP network.

2) The RAT type used by the UE is a specific network type used by theUE, for example, a GERAN network, a UTRAN network, an EUTRAN network, aWLAN network, Wimax network, or a CDMA network.

In step 511, the non-3GPP GW returns an access accept message to the UE.The non-3GPP GW may carry the access policy information of the operatorin the access accept message.

In this embodiment, it should be noted that, the HSS and the AAA servermay be configured in different entities or in the same entity. If theHSS and the AAA server are configured in different entities, theregister message sent by the PDN GW in step 509 is forwarded to the HSSby the AAA server, and the register message sent by the non-3GPP GW inStep 510 is forwarded to the AAA server by the HSS.

FIG. 6 shows a first example of a method for detaching a user when ahandover or change occurs in a heterogeneous network according to anembodiment of the present invention. The method includes the followingsteps.

Steps 601-607 are the same as steps 201-207 in FIG. 2.

In step 608 a, the PDN GW sends a delete bearer request message to theserving GW, and then the serving GW sends the received delete bearerrequest message to the MME, and adds a cause IE in the delete bearerrequest message to indicate the reason of the deletion, and the MMEdeletes the bearer resources.

In this step, as for the bearer deletion caused by the handover orswitching of the UE from the 3GPP network to the non-3GPP network, thePDN GW sets the cause IE as “UE's accessing RAT changed from a 3GPPnetwork to a non-3GPP network”. As for the bearer deletion that is notcaused by the handover or change, the PDN GW sets the cause IE to othervalues. Alternatively, the delete bearer request message sent by the PDNGW does not carry the cause IE, and in this case, once the MME receivesthe delete bearer request message sent by the serving GW, the message isdefaulted to be caused by the handover or switching of the UE from the3GPP network to the non-3GPP network. In this embodiment, the messagecarrying the cause IE is taken as an example.

In this step, it is assumed that an interface protocol between the PDNGW and the serving GW is GPRS tunneling protocol (GTP). If the interfaceprotocol between the PDN GW and the serving GW is the PMIP, step 608 ais replaced by step 608 b, in which the PDN GW sends a bindingrevocation indication message to the serving GW; the cause IE is addedto the binding revocation indication message; the serving GW sends thedelete bearer request message carrying the cause IE sent by the PDN GWto the MME; and the MME deletes the bearer resources after receiving thedelete bearer request message.

As for the binding revocation indication caused by the handover orswitching of the UE from the 3GPP network to the non-3GPP network, thePDN GW sets the cause IE as “UE's accessing RAT changed from a 3GPPnetwork to a non-3GPP network”. As for the bearer deletion that is notcaused by the handover or change, the PDN GW sets the cause IE to othervalues. Alternatively, the binding revocation indication message sent bythe PDN GW does not carry the cause IE, and in this case, once the MMEreceives the delete bearer request message sent by the serving GW, themessage is default to be caused by the handover or switching of the UEfrom the 3GPP network to the non-3GPP network. In this embodiment, themessage carrying the cause IE is taken as an example.

Step 608 a or step 608 b further includes the following: the MME deletesthe bearer resources after receiving the delete bearer request message.If the MME finds that all bearer resources of the UE are deleted, theMME further determines whether to delete an MM context (i.e., detachingthe UE from the 3GPP network) and whether to send a detach requestmessage to the UE. Specifically, the process includes the followingcircumstances.

1) The MME makes the following determination according to the cause IEcarried in the delete bearer request. The MME determines whether thecause IE carried in the received delete bearer request message isrepresented as “UE's accessing RAT changed from a 3GPP network to anon-3GPP network”; if yes, the MME deletes the MM context of the UE, anddoes not send the detach request message to the UE; otherwise, the MMEsends the detach request message to the UE and notifies the UE to deletethe MM context and the bearer resources of the 3GPP network in the UE.

2) The MME makes the following determination according to the IE carriedin the delete bearer request and the terminal capability of the UE. Ifthe MME determines that the IE carried in the received delete bearerrequest message is represented as “UE's accessing RAT changed from a3GPP network to a non-3GPP network”, and the MME knows that the terminalcapability of the UE is “single radio capability”, the MME deletes theMM context of the UE, and does not send the detach request message tothe UE; as for the bearer deletion caused by other reasons, the MMEdeletes the MM context of the UE, and sends the detach request messageto the UE. If the MME knows that the terminal capability of the UE is“multi radio capability”, the MME does not delete the MM context of theUE (that is, does not detach the UE from the 3GPP network).

3) The MME makes the following determination according to the IE carriedin the delete bearer request and the access policy information of theoperator. If the MME determines that the IE carried in the receiveddelete bearer request message is represented as “UE's accessing RATchanged from a 3GPP network to a non-3GPP network”, and the MME knowsthat the access policy information of the operator is “single radioaccess”, the MME deletes the MM context of the UE, and does not send thedetach request message to the UE; as for the bearer deletion caused byother reasons, the MME deletes the MM context of the UE, and sends thedetach request message to the UE. If the MME knows that the accesspolicy information of the operator is “multi radio access”, the MME doesnot delete the MM context of the UE (that is, does not detach the UEfrom the 3GPP network).

4) The MME makes the following determination according to the IE carriedin the delete bearer request, the terminal capability of the UE, and theaccess policy information of the operator. If the MME determines thatthe IE carried in the received delete bearer request message isrepresented as “UE's accessing RAT changed from a 3GPP network to anon-3GPP network”, the terminal capability of the UE is “dual radiocapability”, and the access policy information of the operator is“single radio access”, or if the MME determines that the IE carried inthe received delete bearer request message is represented as “UE'saccessing RAT changed from a 3GPP network to a non-3GPP network”, theaccess policy information of the operator is “multi radio access”, andthe terminal capability of the UE is “single radio capability”, or ifthe MME determines that the IE carried in the received delete bearerrequest message is represented as “UE's accessing RAT changed from a3GPP network to a non-3GPP network”, the terminal capability of the UEis “single radio capability”, and the access policy information of theoperator is “single radio access”, the MME deletes the MM context of theUE, and does not send the detach request message to the UE; as for thebearer deletion caused by other reasons, the MME deletes the MM contextof the UE, and sends the detach request message to the UE. If the MMEknows that the terminal capability of the UE is “dual radio capability”and the access policy information of the operator is “multi radioaccess”, the MME does not delete the MM context of the UE (that is, doesnot detach the UE from the 3GPP network).

In step 609 a, the MME returns a delete bearer response message to theserving GW, and the serving GW returns the delete bearer responsemessage to the PDN GW.

In this step, the interface protocol between the PDN GW and the servingGW is the GIP, and if the interface protocol between the PDN GW and theserving GW is the PMIP, Step 609 a is replaced by step 609 b, in whichthe MME returns the delete bearer response message to the serving GW,and the serving GW returns a binding revocation Ack message to the PDNGW.

In step 610, if the MME sends the detach request message to the UE, theUE deletes the MM context and the bearer resources after receiving thedetach request message, and returns a Detach Accept message to the MME.

In step 611, if the MME finds that the subscription data and the MMcontext of the UE are deleted, the MME sends a purge UE message to theHSS/AAA server, and the HSS/AAA server purges the record of the UE, andreturns a purge UE Ack message to the MME.

In this step, it is determined whether to delete the subscription dataof the UE by the MME according to the actual conditions. This step isoptional.

In the above embodiment, after step 607, it is determined whether todetach the UE from the 3GPP network. Specifically, the determinationprocess is described as follows: according to the handover or change inthe access network, or according to the handover or change of the UE inthe access network and the terminal capability of the UE, or accordingto the handover or change of the UE in the access network and the accesspolicy information of the operator, or according to the handover orchange of the UE in the access network, the terminal capability of theUE, and the access policy information of the operator, it is determinedwhether to detach the UE from the 3GPP network, which particularlyincludes the following four circumstances.

1) It is determined whether the UE is handed over or switched from the3GPP network to the non-3GPP network; if yes, the MM context and bearerresources used by the UE in the 3GPP network are deleted.

2) It is determined whether the UE is handed over or switched from the3GPP network to the non-3GPP network and whether the terminal capabilityof the UE is “single radio capability”; if yes, the bearer resources andthe MM context used by the UE in the 3GPP network are deleted.

3) It is determined whether the UE is handed over or switched from the3GPP network to the non-3GPP network and whether the access policyinformation of the operator is “single radio access”; if yes, the bearerresources and the MM context used by the UE in the 3GPP network aredeleted.

4) It is determined whether the handover or change of the UE in theaccess network, the terminal capability of the UE, and the access policyinformation of the operator satisfy one of the following threeconditions: 1. the UE is handed over or switched from the 3GPP networkto the non-3GPP network, the terminal capability of the UE is “dualradio capability”, and the access policy information of the operator is“single radio access”; 2. the UE is handed over or switched from the3GPP network to the non-3GPP network, the access policy information ofthe operator is “multi radio access”, and the terminal capability of theUE is “single radio capability”; and 3. the UE is handed over orswitched from the 3GPP network to the non-3GPP network, the terminalcapability of the UE is “single radio capability”, and the access policyinformation of the operator is “single radio access”.

If yes, the bearer resources and the MM context used by the UE in the3GPP network are deleted.

Moreover, the delete bearer request added with the cause IE in step 608may be replaced by another message, for example, replaced by a releasebearer request message. The release bearer request message indicatesthat the reason for deleting the bearer is the handover or switching ofthe UE from the 3GPP network to the non-3GPP network; alternatively, thedelete bearer request message sent in step 608 does not carry the reasonfor deleting the bearer, and when the UE is handed over or switched fromthe 3GPP network to the non-3GPP network, a normal delete bearer requestis sent to the MME. In step 608, after receiving the specific message orthe normal delete bearer request message, the MME deletes the bearerresources; and the operations of the MME after the bearer resources aredeleted are similar to the operations of the MME after receiving thedelete bearer request message.

As for the first embodiment, it should be noted that the detachmentmethod in this embodiment is also applicable to the handover orswitching of the UE from a non-3GPP network to a 3GPP network.

In step I, after the UE is handed over or switched to a 3GPP network,the PDN GW sends the binding revocation indication message to a non-3GPPGW. The message carries the cause IE indicating the reason for thebinding revocation. As for the binding revocation caused by the handoveror switching from the non-3GPP network to the 3GPP network, the PDN GWsets the cause IE as “UE's accessing RAT changed from a non-3GPP networkto a 3GPP network”; and as for the binding revocation that is not causedby the handover or change, the PDN GW sets the cause IE to other values.

In step II, the non-3GPP GW deletes the bearer resources after receivingthe binding revocation indication message. If the non-3GPP GW finds thatall bearer resources of the UE are deleted, the non-3GPP GW furtherdetermines whether to delete the MM context of the UE (that is, todetach the UE from the non-3GPP network), which specifically includesthe following circumstances.

1) The non-3GPP GW makes the following determination according to theCause IE carried in the binding revocation indication message, in whichthe non-3GPP GW determines whether the cause IE carried in the bindingrevocation indication message is represented as “UE's accessing RATchanged from a non-3GPP network to a 3GPP network”; if yes, the non-3GPPGW deletes the MM context of the UE, and does not send the detachrequest message to the UE; otherwise, the non-3GPP GW sends the detachrequest message to the UE, and notifies the UE to delete the MM contextand bearer resources of the non-3GPP network in the UE.

2) The non-3GPP GW makes the following determination according to the IEcarried in the binding revocation indication message and the terminalcapability of the UE, in which if the non-3GPP GW determines that the IEcarried in the received binding revocation indication message isrepresented as “UE's accessing RAT changed from a non-3GPP network to a3GPP network”, and the non-3GPP GW knows that the terminal capability ofthe UE is “single radio capability”, the non-3GPP GW deletes the MMcontext of the UE, and does not send the detach request message to theUE; as for the bearer deletion caused by other reasons, the non-3GPP GWdeletes the MM context of the UE, and sends the detach request messageto the UE. If the non-3GPP GW knows that the terminal capability of theUE is “multi radio capability”, the non-3GPP GW does not delete the MMcontext of the UE (that is, does not detach the UE from the non-3GPPnetwork).

3) The non-3GPP GW makes the following determination according to the IEcarried in the binding revocation indication message and the accesspolicy information of the operator, in which if the non-3GPP GWdetermines that the IE carried in the received binding revocationindication message is represented as “UE's accessing RAT changed from anon-3GPP network to a 3GPP network”, and the non-3GPP GW knows that theaccess policy information of the operator is “single radio access”, thenon-3GPP GW deletes the MM context of the UE, and does not send thedetach request message to the UE; as for the bearer deletion caused byother reasons, the non-3GPP GW deletes the MM context of the UE, andsends the detach request message to the UE. If the non-3GPP GW knowsthat the access policy information of the operator is “multi radioaccess”, the non-3GPP GW does not delete the MM context of the UE (thatis, does not detach the UE from the non-3GPP network).

4) The non-3GPP GW makes the following determination according to the IEcarried in the binding revocation indication message, the terminalcapability of the UE, and the access policy information of the operator,in which if the non-3GPP GW determines that the IE carried in thereceived binding revocation indication message is represented as “UE'saccessing RAT changed from a non-3GPP network to a 3GPP network”, theterminal capability of the UE is “dual radio capability”, and the accesspolicy information of the operator is “single radio access”, or if thenon-3GPP GW determines that the IE carried in the received bindingrevocation indication message is represented as “UE's accessing RATchanged from a non-3GPP network to a 3GPP network”, the access policyinformation of the operator is “multi radio access”, and the terminalcapability of the UE is “single radio capability”, or if the non-3GPP GWdetermines that the IE carried in the received binding revocationindication message is represented as “UE's accessing RAT changed from anon-3GPP network to a 3GPP network”, the terminal capability of the UEis “single radio capability”, and the access policy information of theoperator is “single radio access”, the non-3GPP GW deletes the MMcontext of the UE, and does not send the detach request message to theUE; as for the bearer deletion caused by other reasons, the non-3GPP GWdeletes the MM context of the UE, and sends the detach request messageto the UE. If the non-3GPP GW knows that the terminal capability of theUE is “dual radio capability”, and the access policy information of theoperator is “multi radio access”, the non-3GPP GW does not delete the MMcontext of the UE (that is, does not detach the UE from the non-3GPPnetwork).

FIG. 7 shows a second example of the method for user detachment when ahandover or change occurs in a heterogeneous network according to anembodiment of the present invention. The method includes the followingsteps.

Steps 701-707 are the same as steps 201-207 in FIG. 2.

In step 708 a, the PDN GW determines whether to delete the defaultbearer of the UE; if yes, the PDN GW sends the delete bearer requestmessage corresponding to the default bearer to the serving GW, and theserving GW sends the received delete bearer request message to the MME.

The default bearer is a part of the bearer resources.

In this step, the interface protocol between the PDN GW and the servingGW is the GTP. If the interface protocol between the PDN GW and theserving GW is the PMIP, step 708 a is replaced by step 708 b, in whichthe PDN GW sends the binding revocation indication message to theserving GW, and the serving GW determines whether to delete the defaultbearer of the UE; if yes, the serving GW sends the delete bearer requestmessage corresponding to the default bearer to the MME, and the MMEdeletes the MM context and the bearer resources.

In step 708 a or 708 b, the PDN GW/serving GW determines whether todelete the default bearer of the UE in the following manners. The PDNGW/serving GW determines whether to delete the default bearer of the UEaccording to the handover or change of the UE in the access network, oraccording to the handover or change of the UE in the access network andthe terminal capability of the UE, or according to the handover orchange of the UE in the access network and the access policy informationof the operator, or according to the handover or change of the UE in theaccess network, the terminal capability of the UE, and the access policyinformation of the operator. The terminal capability of the UE and theaccess policy information of the operator are obtained by the networkelements according to the flows shown in FIGS. 3 and 4. Specifically,the determination process includes the following circumstances.

1) The PDN GW/serving GW determines whether to delete the default bearerof the UE according to the handover or change of the UE in the accessnetwork, in which the PDN GW/serving GW determines whether the UE ishanded over or switched from the 3GPP network to the non-3GPP network;if yes, the PDN GW/serving GW determines to delete the default bearer ofthe UE, and sends the delete bearer request message corresponding to thedefault bearer to the MME.

2) The PDN GW/serving GW determines whether to delete the default bearerof the UE according to the handover or change of the UE in the accessnetwork and the terminal capability of the UE, in which the PDNGW/serving GW determines whether the UE is handed over or switched fromthe 3GPP network to the non-3GPP network and whether the terminalcapability of the UE is “single radio capability”; if yes, the PDNGW/serving GW determines to delete the default bearer of the UE, andsends the delete bearer request message corresponding to the defaultbearer to the MME.

3) The PDN GW/serving GW determines whether to delete the default bearerof the UE according to the handover or change of the UE in the accessnetwork and the access policy information of the operator, in which thePDN GW/serving GW determines whether the UE is handed over or switchedfrom the 3GPP network to the non-3GPP network and whether the accesspolicy information of the operator is “single radio access”; if yes, thePDN GW/serving GW determines to delete the default bearer of the UE, andsends the delete bearer request message corresponding to the defaultbearer to the MME.

4) The PDN GW/serving GW determines whether to delete the default bearerof the UE according to the handover or change of the UE in the accessnetwork, the terminal capability of the UE, and the access policyinformation of the operator, in which the PDN GW/serving GW determineswhether the handover or change of the UE in the access network, theterminal capability of the UE, and the access policy information of theoperator satisfy one of the following three conditions: 1. the UE ishanded over or switched from the 3GPP network to the non-3GPP network,the terminal capability of the UE is “dual radio capability”, and theaccess policy information of the operator is “single radio access”; 2.the UE is handed over or switched from the 3GPP network to the non-3GPPnetwork, the access policy information of the operator is “multi radioaccess”, and the terminal capability of the UE is “single radiocapability”; and 3. the UE is handed over or switched from the 3GPPnetwork to the non-3GPP network, the terminal capability of the UE is“single radio capability”, and the access policy information of theoperator is “single radio access”.

If yes, the PDN GW/serving GW determines to delete the default bearer ofthe UE, and sends the delete bearer request message corresponding to thedefault bearer to the MME.

In step 709 a, the MME returns a delete bearer response message to theserving GW, and the serving GW returns the delete bearer responsemessage to the PDN GW.

In this step, the interface protocol between the PDN GW and the servingGW is the GTP. If the interface protocol between the PDN GW and theserving GW is the PMIP, step 709 a is replaced by step 709 b, in whichthe MME returns the delete bearer response message to the serving GW,and the serving GW returns the binding revocation Ack message to the PDNGW.

In step 710, if the MME finds that the default bearer of the UE isdeleted, the MME deletes the MM context of the UE (that is, the MMEdetaches the UE from the 3GPP network).

If the MME finds that the subscription data and the MM context of the UEare deleted, the MME sends a purge UE message to the HSS/AAA server, andthe HSS/AAA server purges the record of the UE, and returns a purge UEAck message to the MME.

In this step, it is determined whether to delete the subscription dataof the UE by the MME according to the actual conditions. This step isoptional.

Step 709 and step 710 may be performed at any order.

In the above embodiment, the UE is detached after step 707. Thedetachment process is as follows: according to the handover or change ofthe UE in the access network, or according to the handover or change ofthe UE in the access network and the terminal capability of the UE, oraccording to the handover or change of the UE in the access network andthe access policy information of the operator, or according to thehandover or change of the UE in the access network, the terminalcapability of the UE, and the access policy information of the operator,the UE determines whether to perform the detachment, which specificallyincludes the following four circumstances.

1) It is determined whether the UE is handed over or switched from the3GPP network to the non-3GPP network; if yes, the UE also deletes thedefault bearer, and deletes the MM context and bearer resources used bythe UE in the 3GPP network (that is, the UE is detached from the 3GPPnetwork); otherwise, the UE does not delete the default bearer, and doesnot delete the MM context used by the UE in the 3GPP network.

2) It is determined whether the UE is handed over or switched from the3GPP network to the non-3GPP network and whether the terminal capabilityof the UE is “single radio capability”; if yes, the UE also deletes thedefault bearer, and deletes the MM context and bearer resources used bythe UE in the 3GPP network (that is, the UE is detached from the 3GPPnetwork); otherwise, the UE does not delete the default bearer, and doesnot delete the MM context used by the UE in the 3GPP network.

3) It is determined whether the UE is handed over or switched from the3GPP network to the non-3GPP network and whether the access policyinformation of the operator is “single radio access”; if yes, the UEalso deletes the default bearer, and deletes the MM context and bearerresources used by the UE in the 3GPP network (that is, the UE isdetached from the 3GPP network); otherwise, the UE does not delete thedefault bearer, and does not delete the MM context used by the UE in the3GPP network.

4) It is determined whether the handover or change of the UE in theaccess network, the terminal capability of the UE, and the access policyinformation of the operator satisfy one of the following threeconditions: 1. the UE is handed over or switched from the 3GPP networkto the non-3GPP network, the terminal capability of the UE is “dualradio capability”, and the access policy information of the operator is“single radio access”; 2. the UE is handed over or switched from the3GPP network to the non-3GPP network, the access policy information ofthe operator is “multi radio access”, and the terminal capability of theUE is “single radio capability”; and 3. the UE is handed over orswitched from the 3GPP network to the non-3GPP network, the terminalcapability of the UE is “single radio capability”, and the access policyinformation of the operator is “single radio access”.

If yes, the UE deletes the default bearer, and deletes the MM contextand bearer resources used by the UE in the 3GPP network (that is, the UEis detached from the 3GPP network); otherwise, the UE does not deletethe default bearer, and does not delete the MM context used by the UE inthe 3GPP network.

FIG. 8 shows a third example of the method for user detachment when ahandover or change occurs in a heterogeneous network according to anembodiment of the present invention. The method includes the followingsteps.

Steps 801-807 are the same as steps 201-207 in FIG. 2.

In step 808 a, the PDN GW sends a detach request message to the MMEthrough the serving GW, and the detach request message carries a causevalue represented as “detach because of UE's accessing RAT changed froma 3GPP network to a non-3GPP network”, which indicates that the detachrequest message is caused by the handover or switching of the UE fromthe 3GPP network to the non-3GPP network.

In this step, no interface exists between the PDN GW and the MME. If aninterface exists between the PDN GW and the MME, step 808 a is replacedby step 808 b, in which the PDN GW sends a Detach Request message to theMME, and the Detach Request message carries a Cause value represented as“Detach because of UE's accessing RAT changed from a 3GPP network to anon-3GPP network”, indicating that the detach request message is causedby the handover or change of the UE from the 3GPP network to thenon-3GPP network.

If the interface protocol between the PDN GW and the MME is the PMIP,step 808 a is replaced by step 808 c, in which the PDN GW sends abinding revocation Ind message to the serving GW, and the serving GWsends the detach request message to the MME, and the detach requestmessage carries a cause value represented as “detach because of UE'saccessing RAT changed from a 3GPP network to a non-3GPP network”,indicating that the detach request message is caused by the handover orchange of the UE from the 3GPP network to the non-3GPP network.

In step 808 a, 808 b, or 808 c, before the detach request message issent, the process further includes determining whether to send thedetach request message according to the handover or change of the UE inthe access network, or according to the handover or change of the UE inthe access network and the terminal capability of the UE, or accordingto the handover or change of the UE in the access network and the accesspolicy information of the operator, or according to the handover orchange of the UE in the access network, the terminal capability of theUE, and the access policy information of the operator; if yes, thedetach request message is sent to the MME; otherwise, the process ends.In steps 808 a and 808 b, the determination is performed by the PDN GW,and in step 808 c, the determination is performed by the serving GW.Whether to send the detach request message may be determined accordingto the following circumstances.

1) The PDN GW/serving GW determines whether to send the detach requestmessage to the MME according to the handover or change of the UE in theaccess network, in which the PDN GW/serving GW determines whether the UEis handed over from the 3GPP network to the non-3GPP network; if yes,the detach request message is sent to the MME; otherwise, the processends.

2) The PDN GW/serving GW determines whether to send the detach requestmessage to the MME according to the handover or change of the UE in theaccess network and the terminal capability of the UE, in which the PDNGW/serving GW determines whether the UE is handed over or switched fromthe 3GPP network to the non-3GPP network and whether the terminalcapability of the UE is “single radio capability”; if yes, the detachrequest message is sent to the MME; otherwise, the process ends.

3) The PDN GW/serving GW determines whether to send the detach requestmessage to the MME according to the handover or change of the UE in theaccess network and the access policy information of the operator, inwhich the PDN GW/serving GW determines whether the UE is handed over orswitched from the 3GPP network to the non-3GPP network and whether theaccess policy information of the operator is “single radio access”; ifyes, the detach request message is sent to the MME; otherwise, theprocess ends.

4) The PDN GW/serving GW determines whether to send the detach requestmessage to the MME according to the handover or change of the UE in theaccess network, the terminal capability of the UE, and the access policyinformation of the operator, in which the PDN GW/serving GW determineswhether the handover or change of the UE in the access network, theterminal capability of the UE, and the access policy information of theoperator satisfy one of the following three conditions: 1. the UE ishanded over or switched from the 3GPP network to the non-3GPP network,the terminal capability of the UE is “dual radio capability”, and theaccess policy information of the operator is “single radio access”; 2.the UE is handed over or switched from the 3GPP network to the non-3GPPnetwork, the access policy information of the operator is “multi radioaccess”, and the terminal capability of the UE is “single radiocapability”; and 3. the UE is handed over or switched from the 3GPPnetwork to the non-3GPP network, the terminal capability of the UE is“single radio capability”, and the access policy information of theoperator is “single radio access”.

If yes, the detach request message is sent to the MME; otherwise, theprocess ends.

In step 809 a, the MME receives the detach request message, deletes theMM context, and sends a detach response message to the PDN GW throughthe serving GW.

In this step, no interface exists between the PDN GW and the MME. If aninterface exists between the PDN GW and the MME, step 809 a is replacedby step 809 b, in which the MME receives the detach request message,deletes the MM context, and directly sends a detach response message tothe PDN GW.

If the interface protocol between the PDN GW and the MME is the PMIP,step 809 a is replaced by step 809 c, in which the PDN GW sends thedetach response message to the serving GW, and the serving GW returns abinding revocation Ack message to the PDN GW.

In step 810, the MME initiates a bearer deletion process to delete thebearer resources used by the UE on the 3GPP network side (including theMME, serving GW, and PDN GW).

In step 811, if the MME finds that the subscription data and the MMcontext of the UE are deleted, the MME sends a purge UE message to theHSS/AAA server, and then the HSS/AAA server purges the record of the UE,and returns a purge UE Ack message to the MME.

In this step, it is determined whether to delete the subscription dataof the UE by the MME according to the actual conditions. This step isoptional.

Step 809 and Step 811 may be performed at any order.

In this embodiment, the UE is detached after step 807, and the detailedprocess thereof can be known with reference to the descriptions of thethird example of the method for user detachment.

In this embodiment, it should be noted that, the detach request messagesent by the PDN GW or serving GW may not carry the cause value.

In this embodiment, it should be noted that, the method in thisembodiment is also applicable to the handover or switching of the UEfrom the non-3GPP network to the 3GPP network.

After the UE is handed over or switched from the non-3GPP network to the3GPP network, the PDN GW determines whether to detach the UE from thenon-3GPP network and whether to send the detach request message to thenon-3GPP GW, which includes determining whether to send the detachrequest message according to the handover or change of the UE in theaccess network, or according to the handover or change of the UE in theaccess network and the terminal capability of the UE, or according tothe handover or change of the UE in the access network and the accesspolicy information of the operator, or according to the handover orchange of the UE in the access network, the terminal capability of theUE, and the access policy information of the operator; if yes, thedetach request message is sent to the non-3GPP GW. The detailed processthereof can be known with reference to the descriptions of the aboveembodiment.

FIG. 9 shows a fourth example of the method for user detachment when ahandover or change occurs in a heterogeneous network according to anembodiment of the present invention. The method includes the followingsteps.

Steps 901-907 are the same as steps 201-207 in FIG. 2.

In step 908, the PDN GW sends a register request message to the HSS/AAAserver, and the message carries an RAT type of the UE.

The value of the RAT Type may be one of the following two circumstances.

The RAT Type may be a 3GPP network, which indicates that the networkthat the UE accesses currently is a 3GPP network; and the RAT Type maybe a non-3GPP network, which indicates that the network that the UEaccesses currently is a non-3GPP network.

The RAT Type of the UE may also be a specific network type, for example,GERAN, UTRAN, or EUTRAN network in the 3GPP networks, or WLAN, Wimax,and CDMA network in the non-3GPP networks.

Step 906 and step 908 may be performed at any order.

In step 909, the HSS/AAA server returns a register response message tothe PDN GW.

In step 910, when the HSS/AAA server determines that the RAT Type of theUE registered last time is inconsistent with that of the UE registeredthis time, the HSS/AAA server sends a cancel location message to theMME, in which the cancel location message carries a cause valuerepresented as “Cancel because of UE's accessing RAT changed from a 3GPPnetwork to a non-3GPP network”, indicating that the cancel location iscaused by the handover or switching of the UE from the 3GPP network tothe non-3GPP network.

In this step, before the cancel location message is sent to the MME, theprocess further includes that the HSS/AAA server determines whether tosend the cancel location message according to the handover or change ofthe UE in the access network, or according to the handover or change ofthe UE in the access network and the terminal capability of the UE, oraccording to the handover or change of the UE in the access network andthe access policy information of the operator, or according to thehandover or change of the UE in the access network, the terminalcapability of the UE, and the access policy information of the operator;if yes, the HSS/AAA server sends the cancel location message to the MME;otherwise, the HSS/AAA server does not send the cancel location messageto the MME, and the process ends. Specifically, the determinationprocess specifically includes the following circumstances.

1) The HSS/AAA server determines whether to send the cancel locationmessage to the MME according to the handover or change of the UE in theaccess network, in which the HSS/AAA server determines whether the UE ishanded over or switched from the 3GPP network to the non-3GPP network;if yes, the HSS/AAA server sends the cancel location message to the MME;otherwise, the HSS/AAA server does not send the cancel location messageto the MME, and the process ends.

2) The HSS/AAA server determines whether to send the cancel locationmessage to the MME according to the handover or switching of the UE inthe access network and the terminal capability of the UE, in which ifthe HSS/AAA server determines that the UE is handed over or switchedfrom the 3GPP network to the non-3GPP network, and the terminalcapability of the UE is “single radio capability”, the HSS/AAA serversends the cancel location message to the MME; if the HSS/AAA serverdetermines that the terminal capability of the UE is “multi radiocapability”, the HSS/AAA server does not send the cancel locationmessage to the MME.

3) The HSS/AAA server determines whether to send the cancel locationmessage to the MME according to the handover or change of the UE in theaccess network and the access policy information of the operator, inwhich if the HSS/AAA server determines that the UE is handed over orswitched from the 3GPP network to the non-3GPP network, and the accesspolicy information of the operator is “single radio access”, the HSS/AAAserver sends the cancel location message to the MME; if the HSS/AAAserver determines that the UE is handed over or switched from the 3GPPnetwork to the non-3GPP network, and the access policy information ofthe operator is “multi radio access”, the HSS/AAA server does not sendthe cancel location message to the MME.

4) The HSS/AAA server determines whether to send the cancel locationmessage to the MME according to the handover or switching of the UE inthe access network, the terminal capability of the UE, and the accesspolicy information of the operator, in which if the HSS/AAA serverdetermines that the UE is handed over or switched from the 3GPP networkto the non-3GPP network, the terminal capability of the UE is “dualradio capability”, and the access policy information of the operator is“single radio access”, or if the HSS/AAA server determines that the UEis handed over or switched from the 3GPP network to the non-3GPPnetwork, the access policy information of the operator is “multi radioaccess”, and the terminal capability of the UE is “single radiocapability”, or if the HSS/AAA server determines that the UE is handedover or switched from the 3GPP network to the non-3GPP network, theterminal capability of the UE is “single radio capability”, and theaccess policy information of the operator is “single radio access”, theHSS/AAA server sends the cancel location message to the MME; if theHSS/AAA server determines that the terminal capability of the UE is“dual radio capability” and the access policy information of theoperator is “multi radio access”, the HSS/AAA server does not send thecancel location message to the MME.

In step 911, after receiving the cancel location message, the MMEdeletes the MM context of the UE, and returns a cancel location Ackmessage to the HSS/AAA server.

In step 912, if the MME finds that the subscription data and the MMcontext of the UE are deleted, the MME sends a purge UE message to theHSS/AAA server, and then the HSS/AAA server purges the record of the UE,and returns a purge UE Ack message to the MME.

In this step, it is determined whether to delete the subscription dataof the UE by the MME according to the actual conditions. This step isoptional.

In step 913, the MME initiates a bearer deletion process to delete thebearer resources used by the UE on the 3GPP network side (including theMME, serving GW, and PDN GW).

In this embodiment, the UE is detached after step 907, and the detailedprocess thereof can be known with reference to the descriptions of thethird example of the method for user detachment.

In this embodiment, it should be noted that, the HSS and the AAA servermay be configured in different entities or in a same entity. When theHSS and the AAA server are configured in different entities, theregister request message sent by the PDN GW in step 908 is forwarded tothe HSS through the AAA server, the register response message sent bythe HSS in step 909 is forwarded to the PDN GW through the AAA server,the cancel location message sent to the MME in step 910 is sent to theMME by the HSS, and the purge UE message sent by the MME in step 912 issent to the HSS. The cancel location message sent by the HSS/AAA servermay not carry the cause value.

In this embodiment, it should be noted that, the method in thisembodiment is also applicable to the handover or switching of the UEfrom a non-3GPP network to a 3GPP network.

In Step I, after the UE is handed over or switched from the non-3GPPnetwork to the 3GPP network, the MME or the PDN GW registers a new RATType of the UE with the HSS/AAA server.

In Step II, if the HSS/AAA server determines that the RAT type of the UEregistered last time is inconsistent with that of the UE registered thistime, the HSS/AAA server determines whether to send the cancel locationmessage to a non-3GPP GW (to notify the non-3GPP GW to detach the UEfrom the non-3GPP network) according to the handover or change of the UEin the access network, or according to the handover or change of the UEin the access network and the terminal capability of the UE, oraccording to the handover or change of the UE in the access network andthe access policy information of the operator, or according to thehandover or change of the UE in the access network, the terminalcapability of the UE, and the access policy information of the operator.If yes, the HSS/AAA server sends the cancel location message to thenon-3GPP GW. The detailed process thereof can be known with reference tothe descriptions of the above embodiment.

FIG. 10 shows a fifth example of the method for user detachment when ahandover or change occurs in a heterogeneous network according to anembodiment of the present invention. The method includes the followingsteps.

In step 1001, the UE accesses a 3GPP access network through the servingGW and the PDN GW.

In step 1002, the UE triggers a handover or switching from the 3GPPnetwork to the non-3GPP network.

In step 1003, the MME sends a handover or switching request (HO Request)message to a non-3GPP GW.

In this step, as for a WLAN system, the non-3GPP GW is an EPDG; as for aWimax system, the non-3GPP GW is an ASN GW; and as for a CDMA system,the non-3GPP GW is an AGW.

In Step 1004, the non-3GPP GW performs a resource create procedure.

In this step, the resource create procedure includes performing theprocesses of user authentication and PMIP tunnel binding.

In step 1005, the non-3GPP GW returns an HO response message to the MME.

In step 1006, the MME sends an HO command message to the UE, andcommands the UE to hand over or switch to an access network of thenon-3GPP network.

In step 1007, the UE sends an access request message to the non-3GPP GW,and is handed over or switched to the non-3GPP network.

In step 1008, the non-3GPP GW returns an access accept message to theUE.

Steps 1001-1008 and the process of the handover or switching of the UEfrom a 3GPP network to a non-3GPP network in the prior art implementfunctions similar to that of steps 201-207 in FIG. 2.

In step 1009, the non-3GPP GW returns an HO complete message to the MME.

In step 1010, the MME returns an HO complete Ack message to the non-3GPPGW.

Step 1010 further includes: determining, by the MME, whether to deletethe MM context of the UE (that is, to detach the UE from the 3GPPnetwork) according to the handover or change of the UE in the accessnetwork, or according to the handover or change of the UE in the accessnetwork and the terminal capability of the UE, or according to thehandover or change of the UE in the access network and the access policyinformation of the operator, or according to the handover or change ofthe UE in the access network, the terminal capability of the UE, and theaccess policy information of the operator; if yes, the MME deletes theMM context of the UE; otherwise, the process ends. Specifically, thedetermination process includes the following four circumstances.

1) The MME determines whether to delete the MM context of the UEaccording to the handover or change of the UE in the access network, inwhich if the MME determines that the UE is handed over or switched fromthe 3GPP network to the non-3GPP network, the MME deletes the MM contextof the UE; otherwise, the MME does not delete the MM context of the UE.

2) The MME determines whether to delete the MM context of the UEaccording to the handover or change of the UE in the access network andthe terminal capability of the UE, in which if the MME determines thatthe UE is handed over or switched from the 3GPP network to the non-3GPPnetwork, and the terminal capability of the UE is “single radiocapability”, the MME deletes the MM context of the UE; if the MMEdetermines that the terminal capability of the UE is “multi radiocapability”, the MME does not delete the MM context of the UE.

3) The MME determines whether to delete the MM context of the UEaccording to the handover or change of the UE in the access network andthe access policy information of the operator, in which if the MMEdetermines that the UE is handed over or switched from the 3GPP networkto the non-3GPP network, and the access policy information of theoperator is “single radio access”, the MME deletes the MM context of theUE; if the MME determines that the access policy information of theoperator is “multi radio access”, the MME does not delete the MMcontext.

4) The MME determines whether to delete the MM context of the UEaccording to the handover or change of the UE in the access network, theterminal capability of the UE, and the access policy information of theoperator, in which if the MME determines that the UE is handed over orswitched from the 3GPP network to the non-3GPP network, the terminalcapability of the UE is “dual radio capability”, and the access policyinformation of the operator is “single radio access”, or if the MMEdetermines that the UE is handed over or switched from the 3GPP networkto the non-3GPP network, the access policy information of the operatoris “multi radio access”, and the terminal capability of the UE is“single radio capability”, or if the MME determines that the UE ishanded over or switched from the 3GPP network to the non-3GPP network,the terminal capability of the UE is “single radio capability”, and theaccess policy information of the operator is “single radio access”, theMME deletes the MM context of the UE; if the MME determines that theterminal capability of the UE is “dual radio capability”, and the accesspolicy information of the operator is “multi radio access”, the MME doesnot delete the MM context of the UE.

In step 1011, if the MME finds that the subscription data and the MMcontext of the UE are deleted, the MME sends a purge UE message to theHSS/AAA server, and then the HSS/AAA server purges the record of the UE,and returns a purge UE Ack message to the MME.

In this step, it is determined whether to delete the subscription dataof the UE by the MME according to the actual conditions. This step isoptional.

In step 1012, the MME initiates a bearer deletion process to delete thebearer resources used by the UE on the 3GPP network side (including theMME, serving GW, and PDN GW).

In this embodiment, the UE is detached after Step 1007, and the detailedprocess thereof can be known with reference to the descriptions of thethird example of the method for user detachment.

In this embodiment, it should be noted that, the method in thisembodiment is also applicable to the handover or switching of the UEfrom the non-3GPP network to the 3GPP network.

In Step I, after the UE is handed over or switched from the non-3GPPnetwork to network, the MME returns an HO complete message to thenon-3GPP GW.

In step II, the non-3GPP GW determines whether to delete the MM contextof the UE (that is, to detach the UE from the non-3GPP network)according to the handover or change of the UE in the access network, oraccording to the handover or change of the UE in the access network andthe terminal capability of the UE, or according to the handover orchange of the UE in the access network and the access policy informationof the operator, or according to the handover or change of the UE in theaccess network, the terminal capability of the UE, and the access policyinformation of the operator; if yes, the non-3GPP GW deletes the MMcontext of the UE. The detailed process thereof can be known withreference to the descriptions of the above embodiment.

FIG. 11 shows a sixth example of the method for user detachment when ahandover or change occurs in a heterogeneous network according to anembodiment of the present invention. The method includes the followingsteps.

Steps 1101-1102 are the same as steps 201-202 in FIG. 2.

In step 1103, the UE sends a detach request message to the MME, and thedetach request message carries a cause value represented as “detachbecause of UE's accessing RAT changed from a 3GPP network to a non-3GPPnetwork”, indicating that the detach request message is caused by thehandover or change of the UE from the 3GPP network to the non-3GPPnetwork.

In this step, before the UE sends the detach request message to MME, theprocess further includes determining whether to detach the UE from the3GPP network according to the handover of the UE in the access network,or according to the handover of the UE in the access network and theterminal capability of the UE, or according to the handover of the UE inthe access network and the access policy information of the operator, oraccording to the handover of the UE in the access network, the terminalcapability of the UE, and the access policy information of the operator.If yes, the UE sends the detach request message to the MME; otherwise,step 1107 is performed. The terminal capability of the UE and the accesspolicy information of the operator are obtained by the network elementsaccording to the processes of FIGS. 3 and 4. Specifically, thedetermination process includes the following circumstances.

1) The UE determines whether to detach the UE from the 3GPP network andwhether to send the detach request message to the MME according to thehandover or change of the UE in the access network, in which the UEdetermines whether the UE is handed over or switched from the 3GPPnetwork to the non-3GPP network; if yes, the MM context and bearerresources of the 3GPP network in the UE are deleted, and the detachrequest message is sent to the MME; otherwise, step 1107 is performed.

2) The UE determines whether to detach the UE from the 3GPP network andwhether to send the detach request message to the MME according to thehandover or change of the UE in the access network and the terminalcapability of the UE, in which if the UE determines that the UE ishanded over or switched from the 3GPP network to the non-3GPP network,and the terminal capability of the UE is “single radio capability”, theMM context and the bearer resources of the 3GPP network in the UE aredeleted, and the detach request message is sent to the MME; if the UEdetermines that the terminal capability of the UE is “multi radiocapability”, the MM context of the 3GPP network in the UE is not deleted(that is, the UE is not detached from the 3GPP network), the detachrequest message is not sent to the MME, and step 1107 is performed.

3) The UE determines whether to detach the UE from the 3GPP network andwhether to send the detach request message to the MME according to thehandover or change of the UE in the access network and the access policyinformation of the operator, in which if the UE determines that the UEis handed over or switched from the 3GPP network to the non-3GPPnetwork, and the access policy information of the operator is “singleradio access”, the MM context and the bearer resources of the 3GPPnetwork in the UE are deleted, and the detach request message is sent tothe MME; if the UE determines that the access policy information of theoperator is “multi radio access”, the MM context of network in the UE isnot deleted (that is, the UE is not detached from the 3GPP network), thedetach request message is not sent to the MME, and step 1107 isperformed.

4) The UE determines whether to detach the UE from the 3GPP networkaccording to the handover or change of the UE in the access network, theterminal capability of the UE, and the access policy information of theoperator, in which if the UE determines that the UE is handed over orswitched from the 3GPP network to the non-3GPP network, the terminalcapability of the UE is “dual radio capability”, and the access policyinformation of the operator is “single radio access”, or if the UEdetermines that the UE is handed over or switched from the 3GPP networkto the non-3GPP network, the access policy information of the operatoris “multi radio access”, and the terminal capability of the UE is“single radio capability”, or if the UE determines that the UE is handedover or switched from the 3GPP network to the non-3GPP network, theterminal capability of the UE is “single radio capability”, and theaccess policy information of the operator is “single radio access”, theMM context and the bearer resources of the 3GPP network in the UE aredeleted, and the detach request message is sent to the MME. If the UEdetermines that the terminal capability of the UE is “dual radiocapability”, and the access policy information of the operator is “multiradio access”, the MM context of the 3GPP network in the UE is notdeleted (that is, the UE is not detached from the 3GPP network), thedetach request message is not sent to the MME, and step 1107 isperformed.

In step 1104, after the MME receives the detach request message, the MMEdeletes the MM context of the UE in the MME, initiates a bearer deletionprocess, and deletes the bearer resources used by the UE on the 3GPPnetwork side.

In this step, the bearer resources used by the UE on the 3GPP networkside include the bearer resources used by the UE in the MME, serving GW,and PDN GW.

In step 1105, if the MME finds that the subscription data and the MMcontext of the UE are deleted, the MME sends a purge UE message to theHSS/AAA server, and then the HSS/AAA server purges the record of the UE,and returns a purge UE Ack message to the MME.

In this step, it is determined whether to delete the subscription dataof the UE by the MME according to the actual conditions. This step isoptional.

In step 1106, the MME sends a Detach Accept message to the UE.

Steps 1107-1111 are the same as steps 203-207 in FIG. 2.

Step 1103 and step 1107 may be performed at any order.

In this embodiment, it should be noted that, the method in thisembodiment is also applicable to the handover or switching of the UEfrom the non-3GPP network to the 3GPP network.

When the UE is handed over from the non-3GPP network to the 3GPPnetwork, the UE determines whether to detach the UE from the non-3GPPnetwork according to the handover of the UE in the access network, oraccording to the handover of the UE in the access network and theterminal capability of the UE, or according to the handover of the UE inthe access network and the access policy information of the operator, oraccording to the handover of the UE in the access network, the terminalcapability of the UE, and the access policy information of the operator.If yes, the UE sends the detach request message to the non-3GPP GW. Thedetailed process thereof can be known with reference to the descriptionof the above embodiment.

It should be noted that, in this embodiment, the serving GW and the PDNGW may be configured in different entities or in the same entity. Whenthe serving GW and the PDN GW are configured in the same entity, themessages between the serving GW and the PDN GW are transmitted in thesame entity. The HSS and the AAA server may be configured in differententities or in the same entity. If the HSS and the AAA server areconfigured in different entities, the MME sends the purge UE message tothe HSS.

In the embodiments of the present invention, if the user detachment iscaused by the handover or change of the UE from the 3GPP network to thenon-3GPP network, after the user detachment, the process may furtherinclude: setting, by the MME of the 3GPP, the state of the UE to aninvalid state. Specifically, the process of setting, by the MME of the3GPP, the state of the UE to an invalid state is implemented as follows.

The MME deletes the subscription date information and the MM context ofthe UE.

Alternatively, the MME retains the subscription data information of theUE, but sets the state of the MME used by the UE to an invalid state.

Alternatively, the state of the MME used by the UE is set to an invalidvalue.

Alternatively, the MME retains the subscription data information of theUE, but sets a change flag location of the MME used by the UE to achanged state.

In the embodiments of the present invention, if the user detachment iscaused by the handover or switching of the UE from the non-3GPP networkto the 3GPP network, after the user detachment, the process may furtherinclude: setting, by the non-3GPP GW of the non-3GPP, the state of theUE to an invalid state. Specifically, the process of setting, by thenon-3GPP GW of the non-3GPP, the state of the UE to an invalid state isimplemented as follows.

The non-3GPP GW deletes the subscription data information and the MMcontext of the UE.

Alternatively, the non-3GPP GW retains the subscription data informationof the user, but sets the state of the non-3GPP GW used by the UE to aninvalid state.

Alternatively, the address of the non-3GPP GW used by the UE is set toan invalid value.

Alternatively, a non-3GPP GW retains the subscription data informationof the user, but sets a change flag position of the non-3GPP GW used bythe UE to a changed state.

FIG. 12 shows a system for user detachment when a handover or changeoccurs in a heterogeneous network according to an embodiment of thepresent invention. The system includes a UE and a network side.

The UE is adapted to be handed over or switched from a source network onthe network side to a target network.

The network side is adapted to hand over or switch the UE from thesource network to the target network to detach the UE from the sourcenetwork.

The UE may include a first handover or change module, and the networkside may include a second handover or change module and a seconddetachment module.

The first handover or change module is adapted to enable the UE to behanded over or switched from the source network to the target network.

The second handover or change module is adapted to enable the networkside to hand over or switch the UE from the source network to the targetnetwork.

The second detachment module is adapted to enable the network side todetach the UE from the source network.

Optionally, the UE includes a first detachment module adapted to detachthe UE from the source network.

Optionally, the UE includes a first detachment determination module anda second detachment determination module disposed on the network side.

The first detachment determination module is adapted to determinewhether to detach the UE from the source network, and if yes, an enableinstruction is sent to the first detachment module to enable the firstdetachment module.

The second detachment determination module is adapted to determinewhether to detach the UE from the source network, and if yes, an enableinstruction is sent to the second detachment module to enable the seconddetachment module. The second detachment determination module may bedisposed in a network element on a network side, such as an MME, a PDNGW, a serving GW, or an HSS/AAA server.

The UE further includes a module for sending terminal capability of a UEand a module for receiving access policy information of an operator, andthe network side further includes a module for receiving the terminalcapability of the UE and a module for sending the access policyinformation of the operator.

The module for sending the terminal capability of the UE is adapted tosend the terminal capability of the UE to the network side, and themodule for receiving the access policy information of the operator isadapted to receive the access policy information of the operator sent bythe network side.

The module for receiving the terminal capability of the UE is adapted toreceive the terminal capability of the UE sent by the UE, and the modulefor sending the access policy information of the operator is adapted tosend the access policy information of the operator to the UE.

Based on the solutions for user detachment when a handover or changeoccurs in a heterogeneous network according to the embodiments of thepresent invention, when the UE is handed over or switched from thesource network on the network side to the target network on the networkside, the source network can detach the UE from the source network, andthe UE can detach the UE from the source network.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present inventionwithout departing from the scope of the invention. In view of theforegoing, it is intended that the present invention cover modificationsand variations of this invention provided that they fall within thescope of the following claims and their equivalents.

What is claimed is:
 1. A method comprising: sending, by a packet datanetwork gateway (PDN GW), a delete bearer request including a causeinformation element (IE) to a serving gateway (GW), the cause IE beingset by the PDN GW to represent that a user equipment's (UE) accessingRAT is changed from a 3GPP network to a non-3GPP network; sending, bythe serving GW, the delete bearer to a mobility management entity (MME);receiving, by the MME, the delete bearer request; deleting, by the MME,a bearer resource of the UE; deleting, by the MME, a mobility management(MM) context of the UE.
 2. The method according to claim 1, whereindeleting, by the MME, the MM context of the UE further comprises:deleting, by the MME, the MM context of the UE without sending a detachrequest message to the UE.
 3. The method according to claim 2, whereindeleting, by the MME, the MM context of the UE without sending a detachrequest message to the UE further comprises: deleting, by the MME, theMM context of the UE without sending a detach request message to the UEbased on the cause IE.
 4. A network device comprising: a processor; anda non-transitory computer-readable storage medium storing a program tobe executed by the processor, the program including instructions for: a)receiving a delete bearer request sent by a serving gateway (GW) of a3GPP network when a handover from the 3GPP network to a non-3GPP networkoccurs, wherein the delete bearer request carries a cause informationelement (IE) which indicates a user equipment (UE) handovers from the3GPP network to the non-3GPP network; b) deleting a bearer resource ofthe UE; and c) deleting a mobility management (MM) context of the UE,wherein the delete bearer request is received from a packet data networkgateway (PDN GW) via the serving GW, and the cause IE is set by the PDNGW to represent that the UE's accessing RAT is changed from a 3GPPnetwork to a non-3GPP network.
 5. The network device according to claim4, wherein in deleting the MM context of the UE, the program includinginstructions for deleting the MM context of the UE without sending adetach request message to the UE.
 6. The network device according toclaim 4, wherein in deleting the MM context of the UE, the programincluding instructions for deleting the MM context of the UE withoutsending a detach request message to the UE based on the cause IE.